1. Field of the Invention
The present invention relates generally to phase shifting circuitry. More specifically, the present invention relates to a phase shifter that can be adjusted digitally, precisely, and independently of process and supply variations.
2. Description of the Related Art
A phase shifter circuit can find wide applications in instrumentation, measurement, communication, and control systems. The literature shows different types of phase shifters, which include frequency-dependent, frequency-independent, and auto-tuning phase shifters. The frequency-dependent phase shifter circuit provides fixed or variable phase shift at a single frequency. On the other hand, a frequency independent phase shifter provides a fixed phase shift over a wide range of frequency. Auto-tuning phase shifter's main application is related to phase calibration. Automatic phase shifters may be used in a transceiver system to compensate phase mismatching. Vector modulation is one of the common realizations for phase shifters, wherein a variable phase shift may be obtained by adding the outputs of multiphase filters having adjustable amplitudes. However, such a scheme disadvantageously introduces a stringent requirement for a wide range and accurate controllability of the output amplitude of a large number of filters. While numerous other phase shift designs are known, none taken either singly or in combination, are seen to describe the instant invention as claimed.
Thus, a wideband programmable phase shifting circuit solving the aforementioned problems is desired.